Chunder means to be sick, it originates from old seafareing days when sailers would get seasick and stick their head out of the porthole in their cabin. As they did this they would shout "Watch Under" to warn people in lower cabins of the forthcoming puke. Over the years this has evolved in Chunder.

When one has too much alcohol in the stomach so they get sick and throw up.

Being sick and vomiting. I believe it originates from "watch under", for when someone vomits from an elevated location.

vomitus horrendous

Australian. To vomit.

Verb: to vomit. Most commonly used when concerning someone who has been sick as a result of heavy alcohol consumption.

to vomit from drinking too much